Method and apparatus for control of cardiac therapy using non-invasive hemodynamic sensor

ABSTRACT

A cardiac rhythm management (CRM) system includes a non-invasive hemodynamic sensing device and an implantable medical device to sense a hemodynamic signal and derive one or more cardiac performance parameters from the hemodynamic signal. The non-invasive hemodynamic sensing device includes at least a portion configured for external attachment to a body in which the implantable medical device is implanted. The one or more cardiac performance parameters are used for various diagnostic, monitoring, and therapy control purposes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to co-pending, commonly assigned, U.S.patent application Ser. No. 10/941,427, entitled “NON-INVASIVE METHODAND APPARATUS FOR CARDIAC PACEMAKER PACING PARAMETER OPTIMIZATION ANDMONITORING OF CARDIAC DYSFUNCTION,” filed on Sep. 15, 2004, which ishereby incorporated herein by reference in its entirety.

TECHNICAL FIELD

This document relates generally to cardiac rhythm management (CRM)systems and particularly, but not by way of limitation, to a systemincluding a non-invasive sensor to sense a hemodynamic signal forcardiac performance monitoring and/or cardiac therapy control.

BACKGROUND

The heart is the center of a person's circulatory system. It includes anelectro-mechanical system performing two major pumping functions. Theleft portions of the heart draw oxygenated blood from the lungs and pumpit to the organs of the body to provide the organs with their metabolicneeds for oxygen. The right portions of the heart draw deoxygenatedblood from the body organs and pump it to the lungs where the blood getsoxygenated. These pumping functions are accomplished by cycliccontractions of the myocardium (heart muscles). In a normal heart, thesinoatrial node generates electrical impulses, called action potentials,at a normal sinus rate. The electrical impulses propagate through anelectrical conduction system to various regions of the heart to excitethe myocardial tissues of these regions. Coordinated delays in thepropagations of the action potentials in a normal electrical conductionsystem cause the various portions of the heart to contract in synchronyto result in efficient pumping functions indicated by a normalhemodynamic performance. A blocked or otherwise abnormal electricalconduction and/or deteriorated myocardial tissue cause dysynchronouscontraction of the heart, resulting in poor hemodynamic performanceincluding a diminished blood supply to the heart and the rest of thebody. The condition where the heart fails to pump enough blood to meetthe body's metabolic needs is known as heart failure.

Myocardial infarction (MI) is the necrosis of portions of the myocardialtissue resulted from cardiac ischemia, a condition in which themyocardium is deprived of adequate oxygen and metabolite removal due toan interruption in blood supply caused by an occlusion of a blood vesselsuch as a coronary artery. The necrotic tissue, known as infarctedtissue, loses the contractile properties of the normal, healthymyocardial tissue. Consequently, the overall contractility of themyocardium is weakened, resulting in an impaired hemodynamicperformance. Following an MI, cardiac remodeling starts with expansionof the region of infarcted tissue and progresses to a chronic, globalexpansion in the size and change in the shape of the entire leftventricle. The consequences include a further impaired hemodynamicperformance and a significantly increased risk of developing heartfailure, as well as a risk of suffering recurrent MI.

Cardiac stimulation therapies have been applied to restore functions ofthe electrical conduction system and reduce the deterioration ofmyocardial tissue by delivering electrical pulses to the heart. Theirpotential benefits to a patient are achieved or maximized when suchtherapies are adaptive to the patient's cardiac condition and otherphysiological factors influencing the hemodynamic performance, whichchange over time. A cardiac stimulation therapy may also have unintendedeffects on the hemodynamic performance or cardiac remodeling, with thedegree of impact dependent on the patient's cardiac condition andmetabolic need. In one example, transiently delivering pacing pulses ata relatively high rate may provide a level of hemodynamic performancethat satisfies the patient's instantaneous metabolic need forparticipating in an intense physical activity. However, deliveringpacing pulses at a relatively high rate on a chronic basis may result infurther deterioration of myocardial tissue. In another example, acardiac stimulation therapy preventing further deterioration ofmyocardial tissue may significantly limit the patient's exercisecapacity because the hemodynamic performance is further impaired whentherapy is being delivered.

For these and other reasons, there is a need to modulate the delivery ofcardiac stimulation therapies based on the patient's cardiac conditionsand/or other physiological factors influencing the hemodynamicperformance.

SUMMARY

A CRM system includes a non-invasive hemodynamic sensing device and animplantable medical device to sense a hemodynanic signal and derive oneor more cardiac performance parameters from the hemodynamic signal. Thenon-invasive hemodynamic sensing device includes at least a portionconfigured for external attachment to a body in which the implantablemedical device is implanted. The one or more cardiac performanceparameters are used for various diagnostic, monitoring, and therapycontrol purposes.

In one embodiment, a system includes a non-invasive hemodynamic sensingdevice and an implantable medical device. The non-invasive hemodynamicsensing device is to be attached to an external appendage of a body andincludes a hemodynamic sensor, a sensor signal processor, and a sensortelemetry circuit. The hemodynamic sensor senses a hemodynamic signal.The sensor signal processor produces hemodynamic data associated withthe hemodynamic signal. The sensor telemetry circuit transmits thehemodynamic data from the non-invasive hemodynamic sensing device to theimplantable medical device. The implantable medical device includes animplant telemetry circuit, an electrical stimulation circuit, and astimulation controller. The implant telemetry circuit receives thehemodynamic data from the non-invasive hemodynamic sensing device. Theelectrical stimulation circuit delivers electrical stimulation to thebody. The stimulation controller controls the delivery of the electricalstimulation using one or more stimulation parameters and includes astimulation parameter adjustment module. The stimulation parameteradjustment module adjusts the one or more stimulation parameters usingthe hemodynamic data.

In one embodiment, a method for delivering electrical stimulation isprovided. A hemodynamic signal is sensed using a non-invasivehemodynamic sensor attached to an external appendage of a body.Hemodynamic data associated with the hemodynamic signal are produced andtransmitted to an implantable medical device through a wirelesscommunication link. One or more stimulation parameters are adjustedusing the hemodynamic data using a stimulation controller of theimplantable medical device. The delivery of the electrical stimulationis controlled using the one or more stimulation parameters. Theelectrical stimulation is delivered from the implantable medical device.

This Summary is an overview of some of the teachings of the presentapplication and not intended to be an exclusive or exhaustive treatmentof the present subject matter. Further details about the present subjectmatter are found in the detailed description and appended claims. Otheraspects of the invention will be apparent to persons skilled in the artupon reading and understanding the following detailed description andviewing the drawings that form a part thereof. The scope of the presentinvention is defined by the appended claims and their legal equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate generally, by way of example, variousembodiments discussed in the present document. The drawings are forillustrative purposes only and may not be to scale.

FIG. 1 is an illustration of an embodiment of a CRM system and portionsof an environment in which the CRM system is used.

FIG. 2 is an illustration of an embodiment of a non-invasive hemodynamicsensing device of the CRM system.

FIG. 3 is an illustration of another embodiment of the non-invasivehemodynamic sensing device of the CRM system.

FIG. 4 is an illustration of another embodiment of the non-invasivehemodynamic sensing device of the CRM system.

FIG. 5 is a block diagram illustrating an embodiment of portions of acircuit of the CRM system.

FIG. 6 is a block diagram illustrating an embodiment of portions of acircuit of a non-invasive hemodynamic sensor of the CRM system.

FIG. 7 is a block diagram illustrating an embodiment of portions of acircuit of an implantable medical device of the CRM system.

FIG. 8 is a block diagram illustrating an embodiment of portions of acircuit of an external system of the CRM system.

FIG. 9 is a block diagram illustrating an embodiment of the externalsystem.

FIG. 10 is a flow chart illustrating a method for operating a CRM systemincluding a non-invasive hemodynamic sensing device and an implantablemedical device.

FIG. 11 is a block diagram illustrating an embodiment of portions of acircuit of an implantable medical device that controls post-MI pacingusing a hemodynamic signal sensed by a non-invasive hemodynamic sensor.

FIG. 12 is a flow chart illustrating a method for controlling post-MIpacing using a non-invasive hemodynamic sensing device and animplantable medical device.

FIG. 13 is a block diagram illustrating an embodiment of portions of acircuit of an implantable medical device that controls neuralstimulation using a hemodynamic signal sensed by a non-invasivehemodynamic sensor.

FIG. 14 is a flow chart illustrating a method for controlling neuralstimulation using a non-invasive hemodynamic sensing device and animplantable medical device.

FIG. 15 is a block diagram illustrating an embodiment of portions of acircuit of an implantable medical device that controls a cardiac therapyto optimize a cardiac performance parameter using a hemodynamic signalsensed by a non-invasive hemodynamic sensor.

FIG. 16 is a flow chart illustrating a method for controlling a cardiactherapy to optimize a cardiac performance parameter using a non-invasivehemodynamic sensing device and an implantable medical device.

FIG. 17 is a block diagram illustrating an embodiment of portions of acircuit of an implantable medical device that controls arrhythmiatreatments using a hemodynamic signal sensed by a non-invasivehemodynamic sensor.

FIG. 18 is a flow chart illustrating a method for detecting and treatingarrhythmias using a non-invasive hemodynamic sensing device and animplantable medical device.

FIG. 19 is a block diagram illustrating an embodiment of portions of acircuit of an implantable medical device providing for acquisition ofhemodynamic information associated with a hemodynamic signal sensed by anon-invasive hemodynamic sensor.

FIG. 20 is a flow chart illustrating a method for acquiring diagnosticdata using a non-invasive hemodynamic sensing device and an implantablemedical device.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and in which is shown byway of illustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that the embodiments may be combined, or that otherembodiments may be utilized and that structural, logical and electricalchanges may be made without departing from the spirit and scope of thepresent invention. References to “an”, “one”, or “various” embodimentsin this disclosure are not necessarily to the same embodiment, and suchreferences contemplate more than one embodiment. The following detaileddescription provides examples, and the scope of the present invention isdefined by the appended claims and their legal equivalents.

This document discusses a cardiac rhythm management (CRM) system thatsenses a hemodynamic signal using a non-invasive hemodynamic sensingdevice configured for attachment to an appendage of a body of a patient.The non-invasive hemodynamic sensing device is attached to the body ofthe patent without the need of incision into the body or removal ofbiological tissue from the body. Once attached to the body, thenon-invasive hemodynamic sensing device transmits the sensed hemodynamicsignal to an implantable medical device for therapeutic and/ordiagnostic uses. In various embodiments, the non-invasive hemodynamicsensing device includes a hemodynamic sensor such as a plethysmographysensor or an oximeter to sense a hemodynamic signal indicative ofarterial blood volume, pulse pressure, blood oxygen saturation, and/orheart rate. In various embodiments, one or more cardiac performanceparameters are derived from the hemodynamic signal and used to adjust oroptimize cardiac and/or neural stimulation therapies, detectarrhythmias, and/or monitor cardiac performance. In various embodiments,the CRM system of the present subject matter allows frequent diagnosesof the patient's cardiac functions and adjustments of therapies inresponse to changes in the patient's cardiac functions without frequentvisits to a physician's office or other healthcare facilities. Forexample, the patient may be instructed to attach the non-invasivehemodynamic sensing device periodically to allow for periodicoptimization of therapy parameters by the implantable medical deviceusing the hemodynamic signal. The non-invasive sensing of thehemodynamic signal provides for simplicity and low power consumption forthe implantable medical device.

FIG. 1 is an illustration of an embodiment of a CRM system 100 andportions of an environment in which system 100 is used. System 100includes a non-invasive hemodynamic sensing device 114, an implantablemedical device 110, a lead system 108, an external system 118, atelemetry link 112 providing for communication between non-invasivehemodynamic sensing device 114 and implantable medical device 110, andanother telemetry link 116 providing for communication betweenimplantable medical device 110 and external system 118.

Non-invasive hemodynamic sensing device 114 includes a hemodynamicsensor that senses a hemodynamic signal. In various embodiments, thehemodynamic signal is indicative of one or more of arterial bloodvolume, pulse pressure, blood oxygen saturation, and heart rate. Atleast a portion of non-invasive hemodynamic sensing device 114 isconfigured for attachment to an external body appendage. In oneembodiment, as illustrated in FIG. 1, non-invasive hemodynamic sensingdevice 114 is a finger clip sensor. In another embodiment, at least aportion of non-invasive hemodynamic sensing device 114 is a clip sensorconfigured for attachment to a toe or an ear. In another embodiment, atleast a portion of non-invasive hemodynamic sensing device 114 is a cuffsensor configured for attachment to an arm or wrist. In one embodiment,non-invasive hemodynamic sensing device 114 includes a plethysmographysensor that senses arterial blood volume over time, from whichperipheral pulse pressure and heart rate can be determined. In anotherembodiment, non-invasive hemodynamic sensing device 114 includes a pulseoximeter that senses blood oxygen saturation. In another embodiment,non-invasive hemodynamic sensing device 114 includes a cuff pressuresensor that senses peripheral blood pressures including systolic anddiastolic pressures, from which a pulse pressure can be calculated.Non-invasive hemodynamic sensing device 114 processes the sensedhemodynamic signal to produce hemodynamic data and transmits thehemodynamic data to implantable medical device 110. The hemodynamic datainclude data representative of the sensed hemodynamic signal and/or oneor more cardiac performance parameters derived from the sensedhemodynamic signal.

In various embodiments, implantable medical device 110 is an implantableCRM device including one or more of a pacemaker, acardioverter/defibrillator, a cardiac resynchronization therapy (CRT)device, a cardiac remodeling control therapy (RCT) device, a neuralstimulator, a drug delivery device or a drug delivery controller, abiological therapy device, and a physiological monitoring device. Asillustrated in FIG. 1, implantable medical device 110 is implanted in abody 102. In various embodiments, lead system 108 includes leads forsensing physiological signals and delivering pacing pulses,cardioversion/defibrillation shocks, neural stimulation pulses,pharmaceutical agents, biological agents, and/or other types of energyor substance for treating cardiac disorders. In one embodiment, leadsystem 108 includes one or more pacing-sensing leads each including atleast one electrode placed in or on a heart 101 for sensing electrogramand/or delivering pacing pulses. In other embodiments, electrodes placedin body 102 but away from heart 101 are used to sense physiologicalsignals and deliver pacing pulses, cardioversion/defibrillation shocks,neural stimulation-pulses, pharmaceutical agents, biological agentsand/or other types of energy or substance for treating cardiacdisorders.

Implantable medical device 110 includes an implant controller 124 thatreceives the hemodynamic data from non-invasive hemodynamic sensingdevice 114 and uses the hemodynamic data for diagnostic and/or therapycontrol purposes. In one embodiment, non-invasive hemodynamic sensingdevice 114 produces the one or more cardiac performance parameters andtransmits data representative of the one or more cardiac performanceparameters to implantable medical device 110. In another embodiment,implantable medical device 110 produces the one or more cardiacperformance parameters using the data representative of the sensedhemodynamic signal transmitted from non-invasive hemodynamic sensingdevice 114. In a further embodiment, implantable medical device 110transmits data representative of the sensed hemodynamic signal and/orthe one or more cardiac performance parameters to external system 118.

Telemetry link 112 is a wireless communication link that provides forcommunication between non-invasive hemodynamic sensing device 114 andimplantable medical device 110. In one embodiment, telemetry link 112 isa radio-frequency (RF) electromagnetic telemetry link. In anotherembodiment, telemetry link 112 is a conductive link that uses body 102as the conducting medium. In a specific embodiment, telemetry link 112is an ultrasonic telemetry link. An example of an ultrasonic telemetrysystem is discussed in U.S. patent application Ser. No. 10/888,956,entitled “METHOD AND APPARATUS OF ACOUSTIC COMMUNICATION FOR IMPLANTABLEMEDICAL DEVICE,” filed on Jul. 9, 2004, assigned to Cardiac Pacemakers,Inc., which is incorporated herein by reference in its entirety. Inanother embodiment, non-invasive hemodynamic sensing device 114communicates with implantable medical device 110 via external system118. That is, external system 118 communicates with non-invasivehemodynamic sensing device 114 through a wired or wireless communicationlink and functions as a repeater.

External system 118 allows a user such as the physician or othercaregiver to control the operation of implantable medical device 110 andobtain information acquired by implantable medical device 110, includingthe data representative of the sensed hemodynamic signal and/or the oneor more cardiac performance parameters. In one embodiment, externalsystem 118 includes a programmer communicating with implantable medicaldevice 110 bi-directionally via telemetry link 116. In anotherembodiment, external system 118 is a patient management system includingan external device communicating with a remote device through atelecommunication network. The external device is within the vicinity ofimplantable medical device 110 and communicates with implantable medicaldevice 110 bi-directionally via telemetry link 116. The remote deviceallows the user to monitor and treat a patient from a distant location.The patient monitoring system is further discussed below, with referenceto FIG. 9.

Telemetry link 116 is a wireless communication link that provides forcommunication between implantable medical device 110 and external system118. The communication includes data transmission from implantablemedical device 110 to external system 118. This includes, for example,transmitting real-time physiological data acquired by implantablemedical device 110, extracting physiological data acquired by and storedin implantable medical device 110, extracting therapy history datastored in implantable medical device 110, and extracting data indicatingan operational status of implantable medical device 110 (e.g., batterystatus and lead impedance). Telemetry link 116 also provides for datatransmission from external system 118 to implantable medical device 110.This includes, for example, programming implantable medical device 110to acquire physiological data, programming implantable medical device110 to perform at least one self-diagnostic test (such as for a deviceoperational status), and programming implantable medical device 110 todeliver at least one therapy. In one embodiment, telemetry link 116 isan inductive telemetry link. In one embodiment, telemetry link 116 is anRF electromagnetic telemetry link. In another embodiment, telemetry link116 is an ultrasonic telemetry link.

FIG. 2 is an illustration of an embodiment of a non-invasive hemodynamicsensing device 214, which is a specific embodiment of non-invasivehemodynamic sensing device 114. Non-invasive hemodynamic sensing device214 includes a finger clip device that includes a hemodynamic sensor, asensor signal processor, a sensor telemetry circuit, and a battery. Atelemetry link 212, which is a specific embodiment of telemetry link112, provides for communication between non-invasive hemodynamic sensingdevice 214 and implantable medical device 110.

FIG. 3 is an illustration of an embodiment of a non-invasive hemodynamicsensing device 314, which is a specific embodiment of non-invasivehemodynamic sensing device 114. Non-invasive hemodynamic sensing device314 includes a sensor 314A and a repeater 314B. Sensor 314A is a fingerclip device that includes a hemodynamic sensor, a signal processor, anda battery. Repeater 314B is a portable device that includes anothersignal processor, a sensor telemetry circuit for communicating withimplantable medical device 110, and another battery. In one embodiment,as illustrated in FIG. 3, a telemetry link 314C provides for wirelesscommunication between sensor 314A and repeater 314B. In an alternativeembodiment, sensor 314A and repeater 314B are electrically connectedusing a cable, eliminating the need for telemetry link 314C and thebattery in the finger clip device. A telemetry link 312, which is aspecific embodiment of telemetry link 112, provides for communicationbetween repeater 314B and implantable medical device 110.

FIG. 4 is an illustration of an embodiment of a non-invasive hemodynamicsensing device 414, which is a specific embodiment of non-invasivehemodynamic sensing device 114. Non-invasive hemodynamic sensing device414 includes a sensor 414A electrically connected to a repeater 414Busing a cable 414C. Sensor 414A is a finger clip device that includes ahemodynamic sensor. Repeater 414B is a portable device that includes asignal processor, a sensor telemetry circuit, and a battery. In oneembodiment, as illustrated in FIG. 4, repeater 414B is incorporated intoa wrist band. A telemetry link 412, which is a specific embodiment oftelemetry link 112, provides for communication between repeater 414B andimplantable medical device 110.

Various specific embodiments of non-invasive hemodynamic sensing device114 are illustrated in FIGS. 2-4 for illustrative but not restrictivepurposes. In various-specific embodiments, non-invasive hemodynamicsensing device 114 includes a hemodynamic sensor that is incorporatedinto a clip device that can be attached on to a body appendage such as afinger, a toe, or an ear or a cuff device that can be attached around aportion of a body appendage such as a limb. In various specificembodiments, non-invasive hemodynamic sensing device 114 includes ahemodynamic sensor, a signal processor, a sensor telemetry circuit, anda battery. These components are distributed in one or more device unitsbased on design and user acceptability considerations.

FIG. 5 is a block diagram illustrating an embodiment of portions of acircuit of CRM system 100, including a non-invasive hemodynamic sensingdevice 514, an implantable medical device 510, and external system 118.Non-invasive hemodynamic sensing device 514 is a specific embodiment ofnon-invasive hemodynamic sensing device 114 and includes a hemodynamicsensor 532, a sensor signal processor 534, and a sensor telemetrycircuit 530. Hemodynamic sensor 532 is configured for attachment to anexternal appendage of body 102 to sense a hemodynamic signal. Sensorsignal processor 534 produces hemodynamic data associated with thehemodynamic signal. Sensor telemetry circuit 530 transmits thehemodynamic data from non-invasive hemodynamic sensing device 514 toimplantable medical device 510 via telemetry link 112. Implantablemedical device 510 includes an implant telemetry circuit 522, anelectrical stimulation circuit 520, and an implant controller 524.Implant telemetry circuit 522 receives the hemodynamic data fromnon-invasive hemodynamic sensing device 514 via telemetry link 112.Electrical stimulation circuit 520 delivers electrical stimulationpulses to heart 101 and/or other portions of body 102. Examples of suchelectrical stimulation pulses include pacing pulses,cardioversion/defibrillation pulses, and neural stimulation pulses.Implant controller 524 is a specific embodiment of implant controller124 and includes a stimulation controller 526. Stimulation controller526 controls the delivery of the electrical stimulation pulses using oneor more stimulation parameters and includes a stimulation parameteradjustment module 528 that adjusts the one or more stimulationparameters using the hemodynamic data.

In one embodiment, hemodynamic sensor 532 is incorporated into a fingerclip device such as one of those illustrated in FIG. 1. In otherembodiments, hemodynamic sensor 532 is incorporated into a toe clipdevice or an ear clip device. In one embodiment, hemodynamic sensor 532is a plethysmography sensor that senses arterial blood volume over time,from which peripheral pulse pressure and heart rate can be determined.In another embodiment, hemodynamic sensor 532 is a pulse oximeter thatsenses blood oxygen saturation.

FIG. 6 is a block diagram illustrating an embodiment of portions of acircuit of a non-invasive hemodynamic sensing device 614, which is aspecific embodiment of non-invasive hemodynamic sensing device 114.Non-invasive hemodynamic sensing device 614 includes hemodynamic sensor532, sensor telemetry circuit 530, a sensor signal processor 634, and abattery 644.

Sensor signal processor 634 produces hemodynamic data associated withthe hemodynamic signal. The hemodynamic data include data representativeof the hemodynamic signal and/or data representative of one or morecardiac performance parameters derived from the hemodynamic signal. Theone or more cardiac performance parameters are each being a measure ofcardiac function. In one embodiment, as illustrated in FIG. 6, sensorsignal processor 634 includes a parameter generator 636 that producesthe one or more cardiac performance parameters from the hemodynamicsignal. Parameter generator 636 includes a pulse pressure generator 638,a blood oxygen saturation generator 640, and a heart rate generator 642.Pulse pressure generator 638 produces a pulse pressure parameterrepresentative of pulse pressure using the hemodynamic signal. Bloodoxygen saturation generator 640 produces a blood oxygen saturationparameter representative of blood oxygen saturation using thehemodynamic signal. Heart rate generator 642 produces a heart rateparameter representative of the heart rate using the hemodynamic signal.In various embodiments, depending on the specific diagnostic and/ortherapeutic needs, parameter generator 636 includes any one or more ofpulse pressure generator 638, blood oxygen saturation generator 640, andheart rate generator 642. In an alternative embodiment, implantablemedical device 110 receives the data representative of the hemodynamicsignal and performs the functions of parameter generator 636.

Battery 644 provides non-invasive hemodynamic sensing device 614 withenergy for its operation. In one embodiment, battery 644 is arechargeable battery. In a specific embodiment, non-invasive hemodynamicsensing device 614 is used intermittently, such as on a periodic basis.A battery charger is provided for charging battery 644 when non-invasivehemodynamic sensing device 614 is not in use.

FIG. 7 is a block diagram illustrating an embodiment of portions of acircuit of an implantable medical device 710, which is a specificembodiment of implantable medical device 110. Implantable medical device710 includes a sensing circuit 746, electrical stimulation circuit 520,implant telemetry circuit 522, a data storage device 750, an implantcontroller 724, and a battery 752.

Sensing circuit 746 senses one or more cardiac signals and/or otherphysiological signals. In various embodiments, the sensed signals areused for control of delivery of electrical stimulation pulses byelectrical stimulation circuit 520 and/or for monitoring cardiacfunctions.

Data storage device 750 stores various data including hemodynamic datareceived from non-invasive hemodynamic sensing device 114 and/orprocessed by implant controller 724. The data are stored for use byimplant controller 724 to control therapy deliveries and/or fortransmission to external system 118 upon request.

Implant controller 724 includes an implant signal processor 748 andstimulation controller 526. Implant signal processor 748 processes thesignals sensed by sensing circuit 746. In one embodiment, in whichnon-invasive hemodynamic sensing device 114 produces the datarepresentative of the hemodynamic signal but does not produce the one ormore cardiac performance parameters using the hemodynamic signal,implant signal processor 748 (instead of sensor signal processor 634)includes parameter generator 636, which produces the one or more cardiacperformance parameters using the data representative of the hemodynamicsignal. Stimulation controller 526 controls the delivery of theelectrical stimulation pulses from electrical stimulation circuit 520using selected signals processed and parameters produced by implantsignal processor 748.

Battery 752 provides implantable medical device 710 with the energy forits operation. The longevity of implantable medical device 710 dependson the power consumption of the device and the life of battery 752.

FIG. 8 is a block diagram illustrating an embodiment of portions of acircuit of an external system 818, which is a specific embodiment ofexternal system 118. External system 818 includes an external telemetrycircuit 854, an external controller 856, and a user interface 858.External telemetry circuit 818 transmits data to, and receives datafrom, implantable medical device 110 via telemetry link 116. Externalcontroller 856 controls the operation of external device 818, includingthe processing of information acquired by and transmitted fromimplantable medical device 110. User interface 858 includes a user inputdevice 860 and a presentation device 862. User input device 858 receiveuser commands from the physician or other caregiver and/or the patient.The user commands include a data retrieval command for retrieving dataselected from the data stored in data storage device 750, including dataassociated with the hemodynamic signal sensed by non-invasivehemodynamic sensing device 114. Presentation device 862 presents variousdiagnostic and therapeutic information, including the hemodynamic signaland/or the one or more cardiac performance parameters derived from thehemodynamic signal.

In one embodiment, external system 818 includes a programmer. In anotherembodiment, external system 818 includes a handheld device for use bythe patient and/or the physician or other caregiver. In anotherembodiment, external system 818 includes a patient management systemsuch as described below with reference to FIG. 9.

FIG. 9 is a block diagram illustrating an embodiment of an externalsystem 918. External system 918 represents a special embodiment ofexternal system 118 in which CRM system 100 includes an external patientmanagement system. As illustrated in FIG. 9, external system 918includes an external device 964, a telecommunication network 966, and aremote device 968. External device 964 is placed within the vicinity ofimplantable medical device 110 and includes external telemetry circuit854 to communicate with implantable medical device 110 via telemetrylink 116. Remote device 968 is in one or more remote locations andcommunicates with external device 964 through network 966, thus allowingthe physician or other caregiver to monitor and treat the patient from adistant location and/or allowing access to various treatment resourcesfrom the one or more remote locations. In one embodiment, network 966 isthe Internet. In one embodiment, remote device 968 includes userinterface 858 to allow the physician or other caregiver to monitor thepatient and/or to start, stop, or adjust a therapy in a location remotefrom the patient.

FIG. 10 is a flow chart illustrating a method for operating a CRM systemincluding a non-invasive hemodynamic sensor and an implantable medicaldevice. One example of such a CRM system is CRM system 100.

A hemodynamic signal is sensed using a non-invasive hemodynamic sensorat 1000. The hemodynamic signal indicates one or more of arterial bloodvolume, pulse pressure, and oxygen saturation of blood. The pulsepressure, in turn, indicates changes in cardiac output. In oneembodiment, the hemodynamic signal includes a plethysmogram. Theplethysmogram is sensed by using light to sense changes in arterialblood volume over time. Peripheral pulse pressure and heart rate aredetermined using the changes in arterial blood volume. In anotherembodiment, the hemodynamic signal includes an oximetry signal. Theoximetry signal is sensed by using light to sense blood oxygensaturation.

Hemodynamic data associated with the hemodynamic signal are produced at1010. In one embodiment, the hemodynamic data include datarepresentative of the sensed hemodynamic signal. The non-invasivehemodynamic sensor produces the data representative of the sensedhemodynamic signal (that are later used by the implantable medicaldevice to produce one or more cardiac performance parameters). Inanother embodiment, the hemodynamic data include data representative ofthe sensed hemodynamic signal and/or data representative of one or morecardiac performance parameters. The non-invasive hemodynamic sensorproduces the one or more cardiac performance parameters using the sensedhemodynamic signal and produces data representative of the sensedhemodynamic-signal and/or data representative of the one or more cardiacperformance parameters. The one or more cardiac performance parametersare each a measure of cardiac function. Examples of such cardiacperformance parameters from the hemodynamic signal include a pulsepressure parameter representative of the pulse pressure, a blood oxygensaturation parameter representative of the blood oxygen saturation, anda heart rate parameter representative of the heart rate.

The hemodynamic data are transmitted to the implantable medical deviceat 1020. In one embodiment, the hemodynamic data are transmitted to theimplantable medical device using RF electromagnetic telemetry. Inanother embodiment, the hemodynamic data are transmitted to theimplantable medical device using ultrasonic telemetry.

Delivery of electrical stimulation pulses is controlled using thehemodynamic data at 1030. The delivery of electrical stimulation pulsesis controlled using one or more stimulation parameters. The one or morestimulation parameters are adjusted using the one or more cardiacperformance parameters. In one embodiment, at least one stimulationparameter of the one or more stimulation parameters is approximatelyoptimized using the one or more cardiac performance parameters.

In one embodiment, steps 1000-1030 are performed according to apredetermined schedule, such as on a periodic basis. This allowsadjustment or optimization of the delivery of the electrical stimulationpulses according to the patient's changing cardiac function and changingdemand for hemodynamic performance. In one embodiment, steps 1000-1030are performed when initiated by the physician or other caregiverfollowing a diagnosis, when initiated automatically by the CRM system,and/or when initiated by the patient who perceives a need to do so.

Example 1 Post-MI Pacing Control

In one embodiment, CRM system 100 provides feedback control to a post-MIpacing therapy using cardiac performance as an input. The post-MI pacingtherapy is delivered to a patient who has suffered MI to controlventricular remodeling by inducing ventricular pre-excitation, thusreducing myocardial loading during systole. An example of such a post-MIpacing therapy is discussed in U.S. Pat. No. 6,973,349, “METHOD ANDAPPARATUS FOR MINIMIZING POST-INFARCT VENTRICULAR REMODELING,” assignedto Cardiac Pacemakers, Inc., which is incorporated herein by referencein its entirety. Such myocardial unloading prevents the myocardium fromfurther deterioration but tend to compromise hemodynamic performance,especially when the patient is active. The feedback control is appliedto balance the myocardial unloading with required cardiac output toensure that the post-MI pacing therapy does not compromise the patient'scardiac performance to an intolerable degree.

FIG. 11 is a block diagram illustrating an embodiment of portions of acircuit of an implantable medical device 1110, which is a specificembodiment of implantable medical device 110. Implantable medical device1110 delivers a post-MI pacing therapy and provides feedback control forthat therapy using the hemodynamic data transmitted from non-invasivehemodynamic sensing device 114. Implantable medical device 1110 includesa sensing circuit 1146, a pacing circuit 1120, implant telemetry circuit522, data storage device 750, implant controller 1124, and battery 752.

Sensing circuit 1146 is a specific embodiment of sensing circuit 746 andsenses one or more electrograms for pacing control. Pacing circuit 1120is a specific embodiment of electrical stimulation circuit 520 anddelivers pacing pulses to heart 101 through lead system 108.

Implant controller 1124 includes an implant signal processor 1148 and apacing controller 1126. Implant signal processor 1148 processes the oneor more electrograms for use by pacing controller 1126 and providespacing controller 1126 with one or more cardiac performance parametersthat are received from non-invasive hemodynamic sensing device 114 orproduced from the hemodynamic data received from non-invasivehemodynamic sensing device 114. Pacing controller 1126 controls thedelivery of the pacing pulses using one or more pacing parameters andincludes a pacing parameter adjustment module 1128. Pacing parameteradjustment module 1128 adjusts the one or more pacing parameters usingthe one or more cardiac performance parameters. In one embodiment,pacing parameter adjustment module 1128 adjusts the one or more pacingparameters to approximately maximize ventricular unloading while thepatient's cardiac output, as indicated by the pulse pressure parameter,does not drop below an intolerable level.

In one embodiment, as illustrated in FIG. 11, pacing parameteradjustment module 1128 includes a pacing switch module 1170 that allowsfor starting, stopping, and adjustment of the delivery of pacing pulsesusing the pulse pressure parameter. Pacing switch module 1170 includes apulse pressure comparator 1172, a pacing safety switch 1174, and apacing mode switch 1176. In other embodiments, pacing parameteradjustment module 1128 includes any one or both of pacing safety switch1174 and pacing mode switch 1176. Pulse pressure comparator 1172compares the pulse pressure parameter to a predetermined threshold pulsepressure. The threshold pulse pressure is a pulse pressure level belowwhich the patient's cardiac output is considered too low. In oneembodiment, pacing safety switch 1174 stops the delivery of the pacingpulses when the pulse pressure parameter is below the predeterminedthreshold pulse pressure. In another embodiment, pacing safety switch1174 stops the delivery of the pacing pulses when the pulse pressureparameter drops below a first predetermined threshold pulse pressure andstarts the delivery of the pacing pulses when the pulse pressureparameter rises above a second predetermined threshold pulse pressure.The first predetermined threshold pulse pressure is lower than thesecond predetermined threshold pulse pressure. In one embodiment, pacingmode switch 1176 switches between a cardiac resynchronization therapy(CRT) mode and a remodeling control therapy (RCT) mode based on thepulse pressure parameter. The CRT mode maximizes synchrony ofventricular contractions by maximizing the pulse pressure. The RCT modelimits ventricular remodeling by providing ventricular unloading. Pacingmode switch 1176 switches between the RCT mode and the CRT mode byswitching between a first set of pacing parameters and a second set ofpacing parameters. In a specific embodiment, pacing mode switch 1176switches between the RCT mode and the CRT mode by switching between AVdelays, interventricular (IV) delays (also referred to as IV offsets andleft ventricular offsets), and/or ventricular pacing sites. In aspecific embodiment, pacing mode switch 1176 switches from the RCT modeto the CRT mode when the pulse pressure parameter is below thepredetermined threshold pulse pressure. In another specific embodiment,pacing switch 1176 switches from the RCT mode to the CRT mode when thepulse pressure parameter is drops below a first predetermined thresholdpulse pressure and switch from the CRT mode to the RCT mode when thepulse pressure parameter rises above a second predetermined thresholdpulse pressure. The first predetermined threshold pulse pressure islower than the second predetermined threshold pulse pressure.

FIG. 12 is a flow chart illustrating a method for controlling post-MIpacing using a non-invasive hemodynamic sensor and an implantablemedical device. In one embodiment, the non-invasive hemodynamic sensoris non-invasive hemodynamic sensing device 114, including any of itsspecific embodiments, and the implantable medical device is implantablemedical device 1110.

Hemodynamic data are received from the non-invasive hemodynamic sensorat 1200. In one embodiment, the hemodynamic data include datarepresentative of one or more cardiac performance parameters. In anotherembodiment, the hemodynamic data include data representative of thesensed hemodynamic signal, and the implantable medical device producesthe one or more cardiac performance parameters using the hemodynamicdata. One or more cardiac signals such as electrograms are sensed at1210 for pacing control. Delivery of pacing pulses is controlled usingone or more pacing parameters at 1220. The one or more pacing parametersare adjusted to start, stop, or adjust the delivery of the pacing pulsesusing the hemodynamic data, including the one or more cardiacperformance parameters, at 1230. In one embodiment, the one or morepacing parameters are adjusted to approximately maximize ventricularunloading while the pulse pressure parameter indicates that thepatient's cardiac output is at a tolerable level.

In one embodiment of step 1230, the pulse pressure parameter is comparedto a predetermined threshold pulse pressure for pacing safety control.In a specific embodiment, the delivery of the pacing pulses is stoppedwhen the pulse pressure parameter is below the predetermined thresholdpulse pressure. In another specific embodiment, the delivery of thepacing pulses is stopped when the pulse pressure parameter drops below afirst predetermined threshold pulse pressure and started when the pulsepressure parameter rises above a second predetermined threshold pulsepressure. The first predetermined threshold pulse pressure is lower thanthe second predetermined threshold pulse pressure. In another embodimentof step 1230, the pulse pressure parameter is compared to apredetermined threshold pulse pressure for pacing mode control. Thepacing mode is switched between a CRT mode and an RCT mode based on thepulse pressure parameter. The mode switching between the RCT mode andthe CRT mode is accomplished by switching between a first set of pacingparameters and a second set of pacing parameters. In a specificembodiment, the mode switching between the RCT mode and the CRT mode isaccomplished by switching between a first AV delay and a second AVdelay. In a specific embodiment, the pacing mode is switched from theRCT mode to the CRT mode when the pulse pressure parameter is below thepredetermined threshold pulse pressure. In another specific embodiment,the pacing mode is switched from the RCT mode to the CRT mode when thepulse pressure parameter drops below a first predetermined thresholdpulse pressure and switched from the CRT mode to the RCT mode when thepulse pressure parameter rises above a second predetermined thresholdpulse pressure. The first predetermined threshold cardiac output islower than the second predetermined threshold pulse pressure.

In various embodiments, the hemodynamic data are used to controlswitching between therapy modes in response to the patient's need orcondition indicated by the hemodynamic data. Examples of such therapymodes include two or more of a bradycardia pacing mode, a CRT mode, anRCT mode, a cardioversion mode, a defibrillation mode, and a neuralstimulation mode.

Example 2 Neural Stimulation Control

In one embodiment, CRM system 100 provides heart rate and pulse pressurefeedback control to a neural stimulation therapy that treatscardiovascular disorders. For example, neural stimulation pulses aredelivered to the vagus nerve of a patient who has abnormally high bloodpressure to lower the patient's blood pressure. The feedback control isapplied to maintain the patient's blood pressure in a desirable range.In another example, neural stimulation pulses are delivered to the vagusnerve of a patient who has suffered MI to control post-MI ventricularremodeling. Such vagal stimulation is known to lower the patient's heartrate and pulse pressure. The feedback control is applied to balance theremodeling control with required cardiac output to ensure that thepost-MI neural stimulation therapy does not compromise the patient'scardiac performance to an intolerable degree.

FIG. 13 is a block diagram illustrating an embodiment of portions of acircuit of an implantable medical device 1310, which is a specificembodiment of implantable medical device 110. Implantable medical device1310 controls neural stimulation using the hemodynamic signal sensed bynon-invasive hemodynamic sensing device 114. In one embodiment,non-invasive hemodynamic sensing device 114 provides for sensing of oneor more cardiac performance parameters when a direct connection to heart101 is not needed for delivering the neural stimulation pulses andtherefore unavailable. In a specific embodiment, in which neuralstimulation is applied to lower blood pressure, non-invasive hemodynamicsensing device 114 includes a cuff pressure sensor configured as an armband or wrist band to sense a peripheral blood pressure signal fromwhich systolic pressure, diastolic pressure, and/or pulse pressure aremeasured. Implantable medical device 1310 includes a sensing circuit1346, a neural stimulation circuit 1320, implant telemetry circuit 522,data storage device 750, implant controller 1324, and battery 752.

Sensing circuit 1346 is a specific embodiment of sensing circuit 746 andsenses one or more cardiac and/or neural signals for neural stimulationcontrol. Neural stimulation circuit 1320 is a specific embodiment ofelectrical stimulation circuit 520 and delivers neural stimulationpulses to one or more nerves of body 102, such as one or more nerves ofthe autonomic nervous system, through lead system 108.

Implant controller 1324 includes an implant signal processor 1348 and aneural stimulation controller 1326. Implant signal processor 1348processes the one or more cardiac and/or neural signals for use byneural stimulation controller 1326 and provides neural stimulationcontroller 1326 with one or more cardiac performance parameters that arereceived from non-invasive hemodynamic sensing device 114 or producedfrom the hemodynamic data received from non-invasive hemodynamic sensingdevice 114. Neural stimulation controller 1326 controls the delivery ofneural stimulation pulses using one or more neural stimulationparameters and includes a neural stimulation parameter adjustment module1328. Neural stimulation parameter adjustment module 1328 adjusts theone or more neural stimulation parameters using the one or more cardiacperformance parameters. In one embodiment, neural stimulation parameteradjustment module 1328 sets the one or more neural stimulationparameters to prevent ventricular remodeling or to decrease the heatrate and/or blood pressure when the heart rate parameter is above thepredetermined threshold heart rate and/or when the pulse pressureparameter is above the predetermined threshold pulse pressure.

In one embodiment, as illustrated in FIG. 13, neural stimulationparameter adjustment module 1328 includes a heart rate comparator 1378,a pulse pressure comparator 1380, and a neural stimulation switch 1382.In other embodiments, neural stimulation parameter adjustment module1328 includes any one of heart rate comparator 1378 and pulse pressurecomparator 1380. Neural stimulation switch 1382 allows for starting,stopping, and adjustment of the delivery of the neural stimulationpulses using any one or both of the heart rate parameter and the pulsepressure parameter. Heart rate comparator 1378 compares the heart rateparameter to a predetermined threshold heart rate. In a specificembodiment, neural stimulation switch 1382 stops the delivery of theneural stimulation pulses when the heart rate parameter is below thepredetermined threshold heart rate. In another specific embodiment,neural stimulation switch 1382 stops the delivery of the neuralstimulation pulses when the heart rate parameter drops below a firstpredetermined threshold heart rate and starts the delivery of the neuralstimulation pulses when the heart rate rises above a secondpredetermined threshold heart rate. The first predetermined thresholdheart rate is lower than the second predetermined threshold heart rate.Pulse pressure comparator 1380 compares the pulse pressure parameter toa predetermined threshold pulse pressure. In a specific embodiment,neural stimulation switch 1382 stops the delivery of the neuralstimulation pulses when the pulse pressure parameter is below thepredetermined threshold pulse pressure. In another specific embodiment,neural stimulation switch stops the delivery of the neural stimulationpulses when the pulse pressure parameter drops below a firstpredetermined threshold pulse pressure and starts the delivery of theneural stimulation pulses when the pulse pressure parameter rises abovea second predetermined threshold pulse pressure. The first predeterminedthreshold pulse pressure is lower than the second predeterminedthreshold pulse pressure.

FIG. 14 is a flow chart illustrating a method for controlling neuralstimulation using a non-invasive hemodynamic sensor and an implantablemedical device. In one embodiment, the non-invasive hemodynamic sensoris non-invasive hemodynamic sensing device 114, including any of itsspecific embodiments, and the implantable medical device is implantablemedical device 1310.

Hemodynamic data are received from the non-invasive hemodynamic sensorat 1400. In one embodiment, the hemodynamic data include datarepresentative of one or more cardiac performance parameters. In anotherembodiment, the hemodynamic data include data representative of thesensed hemodynamic signal, and the implantable medical device producesthe one or more cardiac performance parameters using the datarepresentative of the sensed hemodynamic signal. One or more cardiacand/or neural signals are sensed at 1410 for neural stimulation control.Delivery of neural stimulation pulses is controlled using one or moreneural stimulation parameters at 1420. The one or more neuralstimulation parameters are adjusted to start, stop, or adjust thedelivery of the neural stimulation pulses using the hemodynamic data,including the one or more cardiac performance parameters, at 1430. Inone embodiment, the one or more neural stimulation parameters are set toprevent ventricular remodeling or to decrease the heat rate and/or bloodpressure when the heart rate parameter and/or the pulse pressureparameter indicates that the patient's cardiac output is at a tolerablelevel.

In one embodiment of step 1430, the heart rate parameter is compared toa predetermined threshold heart rate. In a specific embodiment, thedelivery of the neural stimulation pulses is stopped when the heart rateparameter is below the predetermined threshold heart rate. In anotherspecific embodiment, the delivery of the neural stimulation pulses isstopped when the heart rate parameter drops below a first predeterminedthreshold heart rate and started when the heart rate rises above asecond predetermined threshold heart rate. The first predeterminedthreshold heart rate is lower than the second predetermined thresholdheart rate. The pulse pressure parameter is compared to a predeterminedthreshold pulse pressure. In a specific embodiment, the delivery of theneural stimulation pulses is stopped when the pulse pressure parameteris below the predetermined threshold pulse pressure. In another specificembodiment, the delivery of the neural stimulation pulses is stoppedwhen the pulse pressure parameter drops below a first predeterminedthreshold pulse pressure and started when the pulse pressure parameterrises above a second predetermined threshold pulse pressure. The firstpredetermined threshold pulse pressure is lower than the secondpredetermined threshold pulse pressure.

Example 3 Cardiac Performance Optimization

In one embodiment, CRM system 100 provides cardiac performance feedbackcontrol to a cardiac stimulation therapy to optimize cardiac output. Forexample, while delivering CRT, cardiac output is to be optimized byapproximately maximizing a peripheral pulse pressure measured by anon-invasive hemodynamic sensor.

FIG. 15 is a block diagram illustrating an embodiment of portions of acircuit of an implantable medical device 1510, which is a specificembodiment of implantable medical device 110. Implantable medical device1510 controls a cardiac therapy to optimize one or more cardiacperformance parameters using the hemodynamic signal sensed bynon-invasive hemodynamic sensing device 114. Implantable medical device1510 includes a sensing circuit 1546, a cardiac stimulation circuit1520, implant telemetry circuit 522, data storage device 750, implantcontroller 1524, and battery 752.

Sensing circuit 1546 is a specific embodiment of sensing circuit 746 andsenses one or more electrograms for control of cardiac stimulationincluding pacing and cardioversion/defibrillation. Cardiac stimulationcircuit 1520 is a specific embodiment of electrical stimulation circuit520 and includes a pacing circuit 1520A and acardioversion/defibrillation circuit 1520B. Pacing circuit 1520Adelivers pacing pulses to heart 101 though lead system 108.Cardioversion/defibrillation circuit 1520B deliverscardioversion/defibrillation circuit pulses to heart 101 through leadsystem 108.

Implant controller 1524 includes an implant signal processor 1548 and acardiac stimulation controller 1526. Implant signal processor 1548processes the one or more electrograms for use by cardiac stimulationcontroller 1526 and provides cardiac stimulation controller 1526 withone or more cardiac performance parameters that are received fromnon-invasive hemodynamic sensing device 114 or produced from thehemodynamic data received from non-invasive hemodynamic sensing device114. Cardiac stimulation controller 1526 controls the delivery of thepacing pulses using one or more pacing parameters and the delivery ofthe cardioversion/defibrillation pulses using one or morecardioversion/defibrillation parameters. Cardiac stimulation controller1526 includes a cardiac stimulation parameter adjustment module 1528that adjusts the one or more pacing parameters and the one or morecardioversion/defibrillation parameters using the one or more cardiacperformance parameters. In one embodiment, cardiac stimulationadjustment module 1528 adjusts the one or more pacing parameters toapproximately optimize a measure of cardiac function indicated by one ofthe one or more cardiac performance parameters. In one embodiment,cardiac stimulation adjustment module 1528 adjusts the one or morecardioversion/defibrillation parameters to select an approximatelyoptimal type and/or energy level for a cardioversion/defibrillationpulse according to the patient's hemodynamic performance during adetected tachyarrhythmia episode as measured by the one or more cardiacperformance parameters.

In one embodiment, as illustrated in FIG. 15, cardiac stimulationparameter optimization module 1528 includes a pacing parameteroptimization module 1584 that approximately optimizes the one or morepacing parameters using the pulse pressure parameter. Pacing parameteroptimization module 1584 includes an atrioventricular (AV) delayoptimization module 1584A and a pacing site optimization module 1584B.AV delay optimization module 1584A approximately optimizes one or moreAV delays to maximize the value of the pulse pressure parameter. In aspecific embodiment, cardiac stimulation controller 1526 controls thedelivery of the pacing pulses using a plurality of AV delays provided byAV delay optimization module 1584A and collects a plurality of valuesfor the pulse pressure parameter each corresponding to one of the AVdelays. AV delay optimization module 1584A selects an optimal AV delay,such as the AV delay that corresponds to the maximum collected value forthe pulse pressure parameter or the shortest AV delay that does notcause a decrease in the value of the pulse pressure parameter. In afurther specific embodiment, in addition to the AV delays, cardiacstimulation controller 1526 controls the delivery of the pacing pulsesusing a plurality of interventricular (IV) delays. AV delay optimizationmodule 1584A selects an optimal AV delay and an optimal IV delay. Inanother specific embodiment, the pacing pulses are delivered to two ormore ventricular sites through lead system 108. Cardiac stimulationcontroller 1526 controls the delivery of the pacing pulses using aplurality of different pacing sites and/or combinations of pacing sitesprovided by pacing site optimization module 1584B and collects aplurality of values for the pulse pressure parameter each correspondingto one of the pacing sites and/or combinations of pacing sites. Pacingsite optimization module 1584B selects the pacing site or combination ofpacing sites corresponding to the maximum collected value for the pulsepressure parameter as the optimal pacing site or optimal combination ofpacing sites. In another specific embodiment, cardiac stimulationcontroller 1526 controls the delivery of the pacing pulses using aplurality of parameter combinations of two or more of AV delays, IVdelays, and pacing cites provided by pacing parameter optimizationmodule 1584 and collects a plurality of values for the pulse pressureparameter each corresponding to one of the parameter combinations.Pacing parameter optimization module 1584 selects an optimal combinationof an AV delay and one or more pacing sites, such as the combinationcorresponding to the maximum collected value for the pulse pressureparameter.

FIG. 16 is a flow chart illustrating a method for controlling a cardiactherapy to optimize a cardiac performance parameter using a non-invasivehemodynamic sensor and an implantable medical device. In one embodiment,the non-invasive hemodynamic sensor is non-invasive hemodynamic sensingdevice 114, including any of its specific embodiments, and theimplantable medical device is implantable medical device 1510.

Hemodynamic data are received from the non-invasive hemodynamic sensorat 1600. In one embodiment, the hemodynamic data include datarepresentative of one or more cardiac performance parameters. In anotherembodiment, the hemodynamic data include data representative of thesensed hemodynamic signal, and the implantable medical device producesthe one or more cardiac performance parameters using the datarepresentative of the sensed hemodynamic signal. One or more cardiacsignals such as electrograms are sensed at 1610 for cardiac stimulationcontrol. Delivery of cardiac stimulation pulses, such as pacing pulsesand cardioversion/defibrillation pulses, is controlled using one or morecardiac stimulation parameters, such as pacing parameters andcardioversion/defibrillation parameters, at 1620. The one or morecardiac stimulation parameters are adjusted to start, stop, or adjustthe delivery of the cardiac stimulation pulses using the one or morecardiac performance parameters at 1630. In one embodiment, one or morepacing parameters are adjusted to approximately optimize a measure ofcardiac function indicated by one of the one or more cardiac performanceparameters. In one embodiment, one or more cardioversion/defibrillationparameters are adjusted to select an approximately optimal type and/orenergy level for a cardioversion/defibrillation pulse according to thepatient's hemodynamic performance during a detected tachyarrhythmiaepisode as measured by the one or more cardiac performance parameters.

In one embodiment of step 1630, one or more pacing parameters areapproximately optimized using the pulse pressure parameter. The one ormore pacing parameters include one or more AV delays and/or one or morepacing sites. The one or more AV delays and/or the one or more pacingsites are approximately optimized to provide for an optimal cardiacoutput as indicated by an approximately maximum value for the pulsepressure parameter. In a specific embodiment, pacing pulses aredelivered using a plurality of AV delays, and the value of the pulsepressure parameter corresponding to each of the AV delays is recorded.The AV delay corresponding to the maximum recorded value of the pulsepressure parameter is selected as the optimal AV delay. In anotherspecific embodiment, pacing pulses are delivered using a plurality ofdifferent pacing sites and/or combinations of pacing sites, and thevalue of the pulse pressure parameter corresponding to each of thepacing sites and/or combinations of pacing sites is recorded. The pacingsite and/or combination of pacing sites corresponding to the maximumrecorded value of the pulse pressure parameter is selected as theoptimal pacing site or optimal combination of pacing sites. In otherspecific embodiments, pacing pulses are delivered using a plurality ofparameter combinations of two or more of AV delay, IV delay, and pacingsites. The value of the pulse pressure parameter corresponding to eachof the parameter combination is recorded. An optimal parametercombination is selected based on the recorded values of the pulsepressure parameter.

Example 4 Arrhythmia Detection and Treatment

In one embodiment, CRM system 100 provides for detection and treatmentof arrhythmias using hemodynamic status of the patient. For example,arrhythmia is detected using heart rate detected from an intracardiacelectrogram and/or a hemodynamic signal sensed by a non-invasivehemodynamic sensor. The hemodynamic signal also indicates the patient'shemodynamic performance based on which an appropriate or optimalanti-arrhythmia therapy is determined.

FIG. 17 is a block diagram illustrating an embodiment portions of acircuit of an implantable medical device 1710. Implantable medicaldevice 1710 is a specific embodiment of implantable medical device 110and controls arrhythmia detection and treatments using the hemodynamicsignal sensed by non-invasive hemodynamic sensing device 114.Implantable medical device 1710 includes a sensing circuit 1546, cardiacstimulation circuit 1520, implant telemetry circuit 522, data storagedevice 750, implant controller 1724, and battery 752.

Implant controller 1724 includes an implant signal processor 1748 and acardiac stimulation controller 1726. Implant signal processor 1748processes the one or more electrograms for use by cardiac stimulationcontroller 1726 and provides cardiac stimulation controller 1726 withone or more cardiac performance parameters that are received fromnon-invasive hemodynamic sensing device 114 or produced from thehemodynamic data received from non-invasive hemodynamic sensing device114. The one or more cardiac performance parameters provide for anindication of the patient's hemodynamic status that allows adetermination of a need for, and/or an adequate type of, cardiacstimulation therapy. Examples of such cardiac stimulation therapyinclude an anti-bradycardia pacing therapy, an anti-tachycardia pacing(ATP) therapy, a cardioversion therapy, and a defibrillation therapy.Cardiac stimulation controller 1726 controls the delivery of the cardiacstimulation pulses using one or more cardiac stimulation parameters.

In one embodiment, as illustrated in FIG. 17, cardiac stimulationcontroller 1726 includes an arrhythmia detector 1786, a pacingcontroller 1788A, and a cardioversion/defibrillation controller 1788B.Arrhythmia detector 1786 detects an arrhythmia using the one or moreelectrograms and/or the one or more cardiac performance parameters. Inone embodiment, arrhythmia detector 1786 detects the arrhythmias usingthe heart rate parameter and the pulse pressure parameter, both derivedfrom the hemodynamic signal. For example, a detection of tachyarrhythmiais declared when the heart rate parameter exceeds a predeterminedtachyarrhythmia threshold and the pulse pressure parameter drops below apredetermined threshold pulse pressure. In another embodiment,arrhythmia detector 1786 detects the arrhythmias using the heart rateparameter and classifies each detected arrhythmia using the pulsepressure parameter. For example, a detection of tachyarrhythmia isdeclared when the heart rate parameter exceeds a predeterminedtachyarrhythmia threshold, and the detected arrhythmia is classified bythe type of therapy needed according to whether the pulse pressureparameter drops below one or more predetermined threshold pulsepressures. In another embodiment, arrhythmia detector 1786 uses a heartrate parameter representative of a heart rate detected from anelectrogram instead of the heart rate parameter derived from thehemodynamic signal. This ensures continuous arrhythmia detection whennon-invasive hemodynamic sensing device 114 is not attached to thepatient. In one embodiment, arrhythmia detector 1786 uses the one ormore electrograms as primary parameters for arrhythmia detection andclassification and uses the one or more cardiac performance parametersderived from the hemodynamic signal, when available, as secondary orsupplemental parameters for the arrhythmia detection and classification.For example, such secondary or supplemental parameters are used tovalidate an arrhythmia detection and/or classification, to substitutefor the primary parameters when the one or more electrograms are noisy,and/or to provide for a separate signal for detecting ventricularfibrillation (during which electrogram amplitude may be low).

Pacing controller 1788A controls the delivery of pacing pulses accordingto a bradyarrythmia pacing mode or an ATP mode.Cardioversion/defibrillation controller 1788B controls the delivery ofthe cardioversion/defibrillation pulses.

FIG. 18 is a flow chart illustrating a method for detecting and treatingarrhythmias using a non-invasive hemodynamic sensor and an implantablemedical device. In one embodiment, the non-invasive hemodynamic sensoris non-invasive hemodynamic sensing device 114, including any of itsspecific embodiments, and the implantable medical device is implantablemedical device 1710.

Hemodynamic data are received from the non-invasive hemodynamic sensorat 1800. In one embodiment, the hemodynamic data include datarepresentative of one or more cardiac performance parameters. In anotherembodiment, the hemodynamic data include data representative of thesensed hemodynamic signal, and the implantable medical device producesthe one or more cardiac performance parameters using the datarepresentative of the sensed hemodynamic signal. The one or more cardiacperformance parameters indicate occurrences of arrhythmia and/or theeffect of the arrhythmia on the patient's hemodynamic performance. Oneor more cardiac signals such as electrograms are sensed at 1810 forcardiac stimulation control and/or arrhythmia detection. An arrhythmiais detected using at least the one or more cardiac performanceparameters at 1820. This includes the detection of the occurrence of thearrhythmia and the classification of the arrhythmia based on theassociated hemodynamic performance. Delivery of cardiac stimulationpulses, such as pacing pulses and cardioversion/defibrillation pulses,is controlled using one or more cardiac stimulation parameters, such aspacing parameters and cardioversion/defibrillation parameters, to treatthe detected arrhythmia at 1830. The cardiac stimulation parameters areselected or adjusted to treat the detected arrhythmia by delivering, forexample, an anti-bradyarrythmia pacing therapy, an ATP therapy, or acardioversion/defibrillation therapy.

In one embodiment of step 1820, the arrhythmia is detected using theheart rate parameter and the pulse pressure parameter, both derived fromthe hemodynamic signal. In one embodiment, the detection oftachyarrhythmia is declared when the heart rate parameter exceeds apredetermined tachyarrhythmia threshold and the pulse pressure parameterdrops below a predetermined threshold pulse pressure. In anotherembodiment, the detection of tachyarrhythmia is declared when the heartrate parameter exceeds the predetermined tachyarrhythmia threshold, andthe arrhythmia is classified by comparing the pulse pressure parameterto one or more predetermined threshold pulse pressures. In anotherembodiment of step 1820, a heart rate parameter detected from anelectrogram is used instead of the heart rate parameter derived from thehemodynamic signal. In one embodiment, one or more signals sensed by theimplantable medical device, such as one or more electrograms, are usedas primary signal(s) for the arrhythmia detection and classification.The hemodynamic signal sensed by the non-invasive hemodynamic sensor,when available, is used as a secondary or supplemental-signal for thearrhythmia detection and/or classification.

Example 5 Diagnostics

In one embodiment, CRM system 100 provides patient diagnostic data onperipheral blood pressure and oxygen saturation changes over a period oftime, with information on associated therapy settings when one or moretherapies are delivered during that period of time. This provides aphysician or other caregiver with information indicative of a patient'scardiac functions, including cardiac functions in association withvarious physical activities and therapies.

FIG. 19 is a block diagram illustrating an embodiment of portions of acircuit of an implantable medical device 1910, which is a specificembodiment of implantable medical device 110. Implantable medical device1910 provides for acquisition of hemodynamic information associated withthe hemodynamic signal sensed by non-invasive hemodynamic sensing device114 as well as other information associated with the patient'sphysiological conditions and/or physical activities. Such information istransmitted to external system 118 to allow for diagnosis and adjustmentof therapy settings with or without the patient's presence before thephysician or other caregiver. Implantable medical device 1910 includes asensing circuit 1946, electrical stimulation circuit 520, implanttelemetry circuit 522, one or more implantable sensors 1990, datastorage device 750, implant controller 1924, and battery 752.

Sensing circuit 1946 senses one or more cardiac and/or neural signalsthrough lead system 108. Implantable sensor(s) 1990 sense each sense asignal indicative of the patient's cardiac function or another type ofsignal used in assessment of the patient's cardiac function. In variousembodiments, implantable sensor(s) 1990 are each included withinimplantable medical device 1910, incorporated onto the housing ofimplantable medical device 1910, or connected to implantable medicaldevice 1910 through lead system 108 or another lead or cable. In oneembodiment, as illustrated in FIG. 19, implantable sensor(s) 1990include an activity sensor 1992 to sense the patient's level of grossphysical activity, which is used in assessment of the patient's cardiacfunction. In a specific embodiment, activity sensor 1992 includes anaccelerometer. In various other embodiments, implantable sensor(s) 1990include one or more of impedance sensors, acoustic sensors, posturesensors, pressure sensors, blood electrolyte sensors, and blood gassensors.

Implant controller 1924 includes an implant signal processor 1948,stimulation controller 526, arrhythmia detector 1786, a command receiver1994, and a data transmitter 1996. Implant signal processor 1948processes the one or more cardiac and/or neural signals, processes theone or more signals sensed by the one or more implantable sensors 1990,and provides stimulation controller 526 with one or more cardiacperformance parameters that are received from non-invasive hemodynamicsensing device 114 or produced from the hemodynamic signal received fromnon-invasive hemodynamic sensing device 114. Data storage device 750stores data representative of the hemodynamic signal and/or datarepresentative of the one or more cardiac performance parameters. Suchstored data include data representative of the pulse pressure parameter,data representative of the blood oxygen saturation parameter, and datarepresentative of the heart rate parameter. In various embodiments, datastorage device 750 also stores, for example, data representative of thecardiac and/or neural signal(s), data representative of the activitylevel, data representative the information about each of the detectedarrhythmia episodes, and data representative of therapy settings andhistory, including the one or more stimulation parameters. Commandreceiver 1994 receives a data retrieval command entered by the physicianor other caregiver through external system 118 and telemetry link 116.Data transmitter 1996 retrieves data from data storage device 750according to the data retrieval command and causes implant telemetrycircuit 522 to transmit the retrieved data to external system 118through telemetry link 116.

FIG. 20 is a flow chart illustrating a method for acquiring diagnosticdata using a non-invasive hemodynamic sensor and an implantable medicaldevice. In one embodiment, the non-invasive hemodynamic sensor isnon-invasive hemodynamic sensing device 114, including any of itsspecific embodiments, and the implantable medical device is implantablemedical device 1910.

Hemodynamic data are received from the non-invasive hemodynamic sensorat 2000. In one embodiment, the hemodynamic data include datarepresentative of one or more cardiac performance parameters. In anotherembodiment, the hemodynamic data include data representative of thesensed hemodynamic signal, and the implantable medical device producesthe one or more cardiac performance parameters using the datarepresentative of the sensed hemodynamic signal. The one or more cardiacperformance parameters indicate occurrences of arrhythmia and/or theeffect of the arrhythmia on the patient's hemodynamic performance.Examples of the one or more cardiac performance parameters include thepulse pressure parameter, the blood oxygen saturation parameter, and theheart rate parameter.

One or more cardiac signals such as electrograms are sensed at 2010 forcardiac stimulation control, arrhythmia detection, and/or patientmonitoring purposes. One or more physiological signals are sensed usingone or more implantable sensors at 2020. Examples of such one or morephysiological signals includes neural signals, activity level signals,respiratory signals, cardiac or transthoracic impedance signals, heartsound signals, pressure signals, and signals indicative of bloodchemistry. Such signals allow for assessment of the patient's cardiacfunction based on the hemodynamic signal and various factors havinginfluence on the hemodynamic signal. Data representative of thehemodynamic signal and/or the cardiac performance parameter(s) as wellas data representative of the physiological signal(s) and parameter(s)derived from the physiological signal(s) are produced for storage in theimplantable medical device.

In one embodiment, delivery of electrical stimulation pulses from theimplantable medical device is controlled using at least the one or morecardiac performance parameters at 2030. For example, one or morestimulation parameters are adjusted using the one or more cardiacperformance parameters, and the electrical stimulation pulses aredelivered according to the one or more stimulation parameters. Datarepresentative of therapeutic settings, including values of the one ormore stimulation parameters used, are produced for storage in theimplantable medical device.

Arrhythmia episodes are detected and classified using at least the oneor more cardiac performance parameters at 2040. In one embodiment,arrhythmia episodes are detected using the heart rate parameter andclassified using the pulse pressure parameter. The classificationprovides for a basis for determining an appropriate therapy. In anotherembodiment, arrhythmia episodes are detected using the heart ratederived from a cardiac signal such as an electrogram and classifiedusing the pulse pressure parameter. In one embodiment, the one or morecardiac signals are primary signals used for arrhythmia detection andclassification, while the one or more cardiac performance parameters areused as secondary or supplemental signals for the arrhythmia detectionand classification. Data representative of information about each of thedetected arrhythmia episodes are produced for storage in the implantablemedical device.

Data associated with the hemodynamic, cardiac, and other physiologicalsignals, data associated with the detected arrhythmia episodes, and dataassociated with the therapy setting are stored in the implantablemedical device at 2050. A data retrieval command is received at 2060. Inone embodiment, the data retrieval command is indicative of the type ofdata to be retrieved from the implantable medical device. In response tothe data retrieval command, at least a portion of the data stored in theimplantable medical device is retrieved and transmitted from theimplantable medical device to an external system at 2070. The retrievedand transmitted data provide for bases for diagnosing or monitoring thepatient's cardiac functions and for making therapeutic decisions.

In General

It is to be understood that the above detailed description is intendedto be illustrative, and not restrictive. Other embodiments will beapparent to those of skill in the art upon reading and understanding theabove description. The scope of the invention should, therefore, bedetermined with reference to the appended claims, along with the fullscope of equivalents to which such claims are entitled.

1. A system coupled to a body having external appendages, the systemcomprising: a non-invasive hemodynamic sensing device including at leasta portion configured to be attached to one of the external appendages,the non-invasive hemodynamic sensing device including: a hemodynamicsensor to sense a hemodynamic signal allowing for determination of apulse pressure; a sensor signal processor to produce hemodynamic datarepresentative of the hemodynamic signal; and a sensor telemetry circuitto transmit the hemodynamic data from the non-invasive hemodynamicsensing device; and an implantable medical device communicativelycoupled to the non-invasive hemodynamic sensing device, the implantablemedical device including: an implant telemetry circuit to receive thehemodynamic data from the non-invasive hemodynamic sensing device; anelectrical stimulation circuit to deliver electrical stimulation; animplant signal processor adapted to process the hemodynamic data, theimplant signal processor including a parameter generator adapted toproduce one or more cardiac performance parameters using the hemodynamicdata, the one or more cardiac performance parameters including at leasta pulse pressure parameter representative of the pulse pressure; and astimulation controller adapted to control the delivery of the electricalstimulation using one or more stimulation parameters, the stimulationcontroller including a stimulation parameter adjustment module adaptedto adjust the one or more stimulation parameters using the one or morecardiac performance parameters.
 2. The system of claim 1, wherein thehemodynamic sensor is adapted to sense one or more of a signalindicative of arterial blood volume, a signal indicative of pulsepressure, a signal indicative of blood oxygen saturation, and a signalindicative of heart rate.
 3. The system of claim 2, wherein thehemodynamic sensor comprises one of a finger clip sensor, a toe clipsensor, and an ear clip sensor.
 4. The system of claim 2, wherein thehemodynamic sensor comprises a plethysmography sensor.
 5. The system ofclaim 2, wherein the hemodynamic sensor comprises a pulse oximeter. 6.The system of claim 1, wherein the hemodynamic sensor comprises apressure sensor adapted to sense a peripheral blood pressure.
 7. Thesystem of claim 1, wherein the non-invasive hemodynamic sensing devicecomprises a portable repeater coupled to the hemodynamic sensor, theportable repeater including at least portions of the signal processorand the sensor telemetry circuit.
 8. The system of claim 7, comprising afinger clip device and a wrist band, wherein the hemodynamic sensor isincorporated into the finger clip device, and the portable repeater isincorporated into the wrist band.
 9. The system of claim 1, wherein thehemodynamic sensor, the sensor signal processor, and the sensortelemetry circuit are incorporated into a clip device adapted to beattached to the one of the external appendages.
 10. The system of claim9, wherein the parameter generator comprises one or more of: a bloodoxygen saturation generator adapted to produce a blood oxygen saturationparameter representative of blood oxygen saturation; and a heart rategenerator to produce a heart rate parameter representative of heartrate.
 11. The system of claim 9, wherein the stimulation parameteradjustment module comprises a cardiac stimulation parameter adjustmentmodule adapted to adjust one or more pacing parameters of the one ormore stimulation parameters using the one or more cardiac performanceparameters.
 12. The system of claim 9, wherein the implant telemetrycircuit is further adapted to transmit data from the implantable medicaldevice, and the implantable medical device comprises a data storagedevice adapted to store data representative of the one or more cardiacperformance parameters, and further comprising an external systemcommunicatively coupled to the implantable medical device, the externalsystem including: an external telemetry circuit to receive data from theimplantable medical device; a user input device adapted to receive usercommands including a data retrieval command for retrieving data storedin the data storage device of the implantable medical device; and apresentation device to present the retrieved data including at least oneof data representative of the hemodynamic signal and data representativeof the one or more cardiac performance parameters.
 13. The system ofclaim 9, wherein the electrical stimulation circuit comprises a pacingcircuit to deliver pacing pulses, the stimulation controller comprises apacing controller to control the delivery of the pacing pulses using oneor more pacing parameters, and the stimulation parameter adjustmentmodule comprises a pacing parameter adjustment module adapted to adjustthe one or more pacing parameters using the one or more cardiacperformance parameters.
 14. The system of claim 13, wherein the pacingparameter adjustment module is adapted to adjust the one or more pacingparameters to approximately maximize ventricular unloading while thepulse pressure parameter does not drop below a predetermined thresholdpulse pressure.
 15. The system of claim 13, wherein the pacing parameteradjustment module comprises a pacing safety switch adapted to start,stop, or adjust the delivery of the pacing pulses using the one or morecardiac performance parameters.
 16. The system of claim 9, wherein theelectrical stimulation circuit comprises a neural stimulation circuit todeliver neural stimulation pulses, the stimulation controller comprisesa neural stimulation controller to control the delivery of the neuralstimulation pulses using one or more neural stimulation parameters, andthe stimulation parameter adjustment module comprises a neuralstimulation parameter adjustment module adapted to adjust the one ormore neural stimulation parameters using the one or more cardiacperformance parameters.
 17. The system of claim 16, wherein the neuralstimulation parameter adjustment module is adapted to adjust the one ormore neural stimulation parameters for preventing ventricular remodelingwhile the pulse pressure parameter is above a predetermined thresholdpulse pressure.
 18. The system of claim 16, wherein the neuralstimulation parameter adjustment module is adapted to adjust the one ormore neural stimulation parameters using the pulse pressure parameter.19. The system of claim 16, wherein the neural stimulation parameteradjustment module comprises a neural stimulation safety switch adaptedto start, stop, or adjust the delivery of the neural stimulation pulsesusing the one or more cardiac performance parameters.
 20. The system ofclaim 9, wherein the electrical stimulation circuit comprises a cardiacelectrical stimulation circuit to deliver cardiac stimulation pulsesincluding one or more of pacing pulses and cardioversion/defibrillationpulses, and the stimulation controller comprises an arrhythmia detectoradapted to detect and classify arrhythmias using at least the one ormore cardiac performance parameters, the stimulation controller adaptedto control the delivery of the cardiac stimulation pulses to treat thedetected arrhythmias according to the classification of each of thedetected arrhythmias.
 21. The system of claim 1, wherein the stimulationparameter adjustment module comprises a stimulation parameteroptimization module adapted to approximately optimize at least onestimulation parameter of the one or more stimulation parameters usingthe one or more cardiac performance parameters.
 22. A method fordelivering electrical stimulation to a body having external appendages,the method comprising: sensing a hemodynamic signal using a non-invasivehemodynamic sensor attached to one of the external appendages of thebody, the hemodynamic signal allowing for determination of a pulsepressure; producing hemodynamic data representative of the hemodynamicsignal; transmitting the hemodynamic data to an implantable medicaldevice through a wireless communication link; producing one or morecardiac performance parameters using the hemodynamic data using a signalprocessor of the implantable medical device, the one or more cardiacperformance parameters including at least a pulse pressure parameterrepresentative of the pulse pressure; adjusting one or more stimulationparameters using the one or more cardiac performance parameters using astimulation controller of the implantable medical device; controllingthe delivery of the electrical stimulation using the one or morestimulation parameters; and delivering the electrical stimulation fromthe implantable medical device.
 23. The method of claim 22, whereinsensing the hemodynamic signal comprises sensing a hemodynamic signalindicative of at least the pulse pressure and one or more of arterialblood volume, blood oxygen saturation, and heart rate.
 24. The method ofclaim 23, wherein sensing the hemodynamic signal comprises sensing oneor more of a plethysmogram, an oximetry signal, and a blood pressuresignal.
 25. The method of claim 22, wherein producing the one or morecardiac performance parameters comprises producing one or more of ablood oxygen saturation parameter representative of blood oxygensaturation, and a heart rate parameter representative of a heart rate.26. The method of claim 22, wherein producing the one or more cardiacperformance parameters comprises producing the one or more cardiacperformance parameters using a signal processor external to theimplantable medical device, and transmitting the hemodynamic data to theimplantable medical device comprises transmitting the one or morecardiac performance parameters to the implantable medical device. 27.The method of claim 22, wherein adjusting the one or more stimulationparameters comprises approximately optimizing at least one stimulationparameter of the one or more stimulation parameters using the one ormore cardiac performance parameters.
 28. The method of claim 22, furthercomprising: storing one or more of data representative of thehemodynamic signal and data representative of the one or more cardiacperformance parameters in the implantable medical device; receiving usercommands including a data retrieval command; retrieving data includingthe stored one or more of the data representative of the hemodynamicsignal and the data representative of the one or more cardiacperformance parameters; transmitting the retrieved data from theimplantable medical device to an external system via telemetry; andpresenting one or more of the hemodynamic signal and the one or morecardiac performance parameters using a presentation device of theexternal system.
 29. The method of claim 22, wherein delivering theelectrical stimulation comprises delivering cardiac pacing pulses, andcontrolling the delivery of the electrical stimulation using thehemodynamic signal comprises: controlling the delivery of the cardiacpacing pulses using one or more pacing parameters; and adjusting the oneor more pacing parameters using the one or more cardiac performanceparameters.
 30. The method of claim 29, wherein the one or more cardiacperformance parameters comprises a pulse pressure parameterrepresentative of pulse pressure, and adjusting the one or more pacingparameters comprises: comparing the pulse pressure parameter to apredetermined threshold pulse pressure; and adjusting the one or morepacing parameters to approximately maximize ventricular unloading whilethe pulse pressure parameter is above the predetermined threshold pulsepressure.
 31. The method of claim 29, wherein the one or more cardiacperformance parameters comprises a pulse pressure parameterrepresentative of pulse pressure, and adjusting the one or more pacingparameters comprises: comparing the pulse pressure parameter to apredetermined threshold pulse pressure; and stopping the delivery of thepacing pulses when the pulse pressure parameter drops below a firstpredetermined threshold pulse pressure and starting the delivery of thepacing pulses when the pulse pressure parameter rises above a secondpredetermined threshold pulse pressure, the first predeterminedthreshold pulse pressure lower than the second predetermined thresholdpulse pressure.
 32. The method of claim 22, wherein delivering theelectrical stimulation comprises delivering neural stimulation pulses,and controlling the delivery of the electrical stimulation using thehemodynamic signal comprises: controlling the delivery of the neuralstimulation pulses using one or more neural stimulation parameters; andadjusting the one or more neural stimulation parameters using the one ormore cardiac performance parameters.
 33. The method of claim 32, whereinthe one or more cardiac performance parameters comprises at least one ofa pulse pressure parameter representative of pulse pressure and a heartrate parameter representative of heart rate, and adjusting the one ormore pacing parameters comprises: comparing each of the one or morecardiac performance parameters to a corresponding predeterminedthreshold indicative of a tolerable level of hemodynamic performance;and adjusting the one or more pacing parameters to approximatelymaximize ventricular unloading using at least one outcome of thecomparison.
 34. The method of claim 32, wherein the one or more cardiacperformance parameters comprises a pulse pressure parameterrepresentative of pulse pressure, and adjusting the one or more pacingparameters comprises: comparing each of the one or more cardiacperformance parameters to a corresponding predetermined thresholdindicative of a tolerable level of hemodynamic performance; and startingstopping, or adjusting the delivery of the neural stimulation pulsesusing at least one outcome of the comparison.
 35. The method of claim22, wherein delivering the electrical stimulation comprises deliveringcardiac electrical stimulation pulses including at least one of cardiacpacing pulses and cardioversion/defibrillation pulses, and controllingthe delivery of the electrical stimulation using the hemodynamic signalcomprises: controlling the delivery of the cardiac stimulation pulsesusing one or more cardiac stimulation parameters; detecting andclassifying arrhythmias using the one or more cardiac performanceparameters; and adjusting the one or more cardiac stimulation parametersto treat each of the detected arrhythmia according to the classificationof that arrhythmia in response to the detection of that arrhythmia. 36.The method of claim 22, wherein controlling the delivery of theelectrical stimulation comprises switching between therapy modes. 37.The method of claim 36, wherein controlling the delivery of theelectrical stimulation comprises switching between two or more of abradycardia pacing mode, a cardiac resynchronization therapy mode, acardiac remodeling control therapy mode, a cardioversion mode, adefibrillation mode, and a neural stimulation mode.